Towing systems with passenger cars usually comprise a towing passenger car and a trailer, which usually has a body arranged on an axle and is coupled with the towing passenger car via a towbar and a trailer hitch. The trailer hitch is standardized in Europe and comprises a ball head on the motor vehicle side and a ball cup on the trailer side. Many drivers have difficulties during switching in estimating the position of the trailer and in deflecting the system comprising the towed and towing vehicles in the desired direction.
In case of unfavorable loading, defects at the trailer axle and side wind effects, it may happen that the trailer destabilizes the system comprising the towing and towed vehicles due to rolling movements and uncontrolled driving states are provoked.
DE 198 10 378 A1 discloses a trailer hitch with a hitch ball, which is carried by a ball neck and in which a ball opening is provided. An inductive, metal-detecting sensor is held at an insert, which is fixed in the ball opening and has a mount for the sensor. The trailer hitch may consist of a deformable steel, a deformable light metal or even a castable metal, whereas the insert is preferably made of a plastic part. The sensor is designed to detect the coupled or uncoupled state of a hitch mouth. The angle of the hitch mouth relative to the trailer hitch cannot be determined with this arrangement.
DE 198 34 752 C2 pertains to a device for controlling the reverse travel of motor vehicles with trailers, wherein the determination of the relative position of the motor vehicle in relation to the trailer is performed by an eccentric distance measurement by ultrasound at two points. As an alternative, the position of the motor vehicle in relation to the trailer can be determined by an angle measurement in the trailer hitch. However, it is not disclosed how and with what means the angle measurement can be carried out in the trailer hitch. Furthermore, rolling movements of the trailer in relation to the motor vehicle cannot be detected.